1. Field
Example embodiments relate to a method of manufacturing a polymer dispersed liquid crystal (PDLC) display device including a dichroic dye.
2. Description of the Related Art
Conventional polymer dispersed liquid crystal (PDLC) display devices change a refractive index of a polymer and liquid crystals and scatter or transmit light by applying an electric field to a PDLC layer in which the polymer and the liquid crystals are uniformly mixed. The PDLC display device may transmit or reflect light by using only an electric field and without using an alignment layer and a polarizer. In addition, when dichroic dyes are mixed in the PDLC layer, a display device having improved contrast may be realized. When the dichroic dyes are mixed with liquid crystals, the dichroic dyes may be arranged according to the movement of the liquid crystals. Accordingly, when the dichroic dyes are mixed in the PDLC layer, the dichroic dyes may be arranged as a result of the movement of the liquid crystals or may be randomly distributed. Thus, an optical change may occur.
A PDLC display device including dichroic dyes is conventionally manufactured by injecting a mixture solution of liquid crystals, a photopolymerizable material, and dichroic dyes between two electrodes that face each other and by hardening the mixture solution by using ultraviolet rays. The photopolymerizable material denotes a material which becomes a polymer due to a photopolymerization reaction and may include monomers or oligomers. Because of the hardening process using ultraviolet rays, the liquid crystals are uniformly dispersed in the polymer, and the dichroic dyes uniformly exist in the polymer and the liquid crystals. However, the dichroic dyes existing in the polymer may affect optical characteristics of the display device. For instance, the dichroic dyes existing in the polymer may not move due to the hardening process using ultraviolet rays. The immovable dichroic dyes may not have optical anisotropy and, thus, may adversely affect visibility of the display device. In addition, the dichroic dyes existing in the polymer during the hardening process using ultraviolet rays continuously absorbs ultraviolet rays and, thus, may deteriorate hardening characteristics.
To address the above problems, a method of applying an electric field to a mixture solution of liquid crystals, a photopolymerizable material, and dichroic dyes before performing the hardening process using ultraviolet rays and thus uniformly arranging the liquid crystals and the dichroic dyes in the electric field has been introduced. However, in this method, the dichroic dyes may not be arranged in a regular direction in the polymer. In a mixture solution in which the photopolymerizable material (which may be monomers or oligomers), the liquid crystals, and the dichroic dyes are uniformly mixed is prepared, the liquid crystals may lose their electric characteristic in the mixture solution. To arrange the dichroic dyes in a line, the liquid crystals may be first arranged in a line by applying an electric field and then the dichroic dyes are arranged in a line by the movement of the liquid crystals. However, the electric characteristic of the liquid crystals is lost in the mixture solution of the liquid crystals, the photopolymerizable material, and the dichroic dyes.
Thus, even when an electric field is applied to the mixture solution, the dichroic dyes are not arranged in a line but remain randomly arranged in the mixture solution. In order for the liquid crystals to maintain their electric characteristics in the mixture solution, phase separation may occur to some degree in the liquid crystals and the photopolymerizable material after the photopolymerization reaction using ultraviolet rays. However, in the above method, an electric field is applied before the photopolymerization reaction occurs and thus the dichroic dyes existing in the mixture solution may not be arranged in a line even by application of an electric field. Accordingly, in the above method, the dichroic dyes existing in the polymer are not arranged in a line but are arranged randomly even after an electric field is applied and the hardening process using ultraviolet rays is performed. Thus improvements in visibility and ultraviolet rays hardening characteristic may not occur.